A project on the activation of the 7-transmembrane/G-protein coupled human thrombin receptor and its role in platelet aggregation is being done by Dr. Athan Kulopulost. Dr. Kullopulos is studying how platelet aggregation is stimulated by alpha-thrombin which exerts its action by recognizing and cleaving the N-terminal extracellular domain of the receptor located on the platelet membrane. The autolysis products of the extracellular domain have been identified using Edman sequencing and MALDI-TOF-MS. Further work concerns the identification of reaction products generated by thrombin cleavage of a recombinant extracellular domain of thrombin for which MALDI- TOF-MS or ESI-MS will be required.